Haemodynamic effects of prazosin combinations during dynamic and isometric exercise.

Haemodynamic effects of atenolol 50 mg, clonidine 0.15 mg, and prazosin 5 mg, given twice daily, and of the combinations atenolol + prazosin and clonidine + prazosin were studied in 8 hypertensive outpatients. Measurements were made at rest, during isometric sustained handgrip and submaximal ergometer work in mostly double-blind and cross-over fashion. Given individually atenolol and prazosin lowered resting supine blood pressure. The addition of prazosin increased the antihypertensive effects of atenolol but not of clonidine. At the end of the isometric exercise atenolol and prazosin given alone both lowered diastolic blood pressure as compared to respective pretreatment values. During handgrip prazosin contributed a little, but not much, to the antihypertensive effects of atenolol and clonidine. During dynamic exercise atenolol, clonidine, and prazosin given alone each lowered blood pressure, prazosin decreasing diastolic blood pressure in particular. Prazosin added to the antihypertensive effect of atenolol more than that of clonidine. Echocardiographic measurements revealed no significant differences between treatments at rest. During handgrip the mean velocity of left ventricular circumferential muscle fibre shortening was reduced by atenolol as compared to pretreatment values. We conclude that atenolol + prazosin may help the patients to maintain adequate haemodynamics during daily physical stresses whilst the combination prazosin + clonidine may not offer any particular advantages.